'use strict'

// Characters.
var nil = '\0'
var ampersand = '&'
var space = ' '
var tab = '\t'
var graveAccent = '`'
var quotationMark = '"'
var apostrophe = "'"
var equalsTo = '='
var lessThan = '<'
var greaterThan = '>'
var slash = '/'
var lineFeed = '\n'
var carriageReturn = '\r'
var formFeed = '\f'

var whitespace = [space, tab, lineFeed, carriageReturn, formFeed]

// See: <https://html.spec.whatwg.org/#attribute-name-state>.
var name = whitespace.concat(ampersand, slash, greaterThan, equalsTo)

// See: <https://html.spec.whatwg.org/#attribute-value-(unquoted)-state>.
var unquoted = whitespace.concat(ampersand, greaterThan)
var unquotedSafe = unquoted.concat(
  nil,
  quotationMark,
  apostrophe,
  lessThan,
  equalsTo,
  graveAccent
)

// See: <https://html.spec.whatwg.org/#attribute-value-(single-quoted)-state>.
var singleQuoted = [ampersand, apostrophe]

// See: <https://html.spec.whatwg.org/#attribute-value-(double-quoted)-state>.
var doubleQuoted = [ampersand, quotationMark]

// Maps of subsets.
// Each value is a matrix of tuples.
// The first value causes parse errors, the second is valid.
// Of both values, the first value is unsafe, and the second is safe.
module.exports = {
  name: [
    [name, name.concat(quotationMark, apostrophe, graveAccent)],
    [
      name.concat(nil, quotationMark, apostrophe, lessThan),
      name.concat(nil, quotationMark, apostrophe, lessThan, graveAccent)
    ]
  ],
  unquoted: [
    [unquoted, unquotedSafe],
    [unquotedSafe, unquotedSafe]
  ],
  single: [
    [singleQuoted, singleQuoted.concat(quotationMark, graveAccent)],
    [
      singleQuoted.concat(nil),
      singleQuoted.concat(nil, quotationMark, graveAccent)
    ]
  ],
  double: [
    [doubleQuoted, doubleQuoted.concat(apostrophe, graveAccent)],
    [
      doubleQuoted.concat(nil),
      doubleQuoted.concat(nil, apostrophe, graveAccent)
    ]
  ]
}